Touch screens allow a user to conveniently interface with an electronic display system by reducing or eliminating the need for a keyboard. For example, a user can carry out a complicated sequence of instructions by simply touching the screen at a location identified by a pre-programmed icon. The on-screen menu may be changed by re-programming the supporting software according to the application. As another example, a touch screen may allow a user to transfer text or drawing to an electronic display device by directly writing or drawing onto the touch screen.
Resistive and capacitive are two common touch sensing methods employed to detect the location of a touch input. Resistive technology typically incorporates two transparent conductive films as part of an electronic circuit that detects the location of a touch. Capacitive technology, on the other hand, typically uses a single transparent conductive film to detect the location of an applied touch.
Some known capacitive touch sensors include an electrically continuous resistive layer disposed in the touch sensitive area. An example of such a sensor is discussed in U.S. Pat. No. 5,045,644 where orthogonal electric fields are produced on a resistive surface to determine a touch location. Some other known capacitive touch sensors employ an array of electrically conductive electrodes disposed in the touch sensitive area discussed in, for example, U.S. Pat. No. 6,970,160.